Previous studies in our laboratory have implicated fecal bacterial enzymes in the activation of procarcinogens in the intestine. By suppressing the metabolic activity of the microflora with diet (low fat), Lactobacillus feeding, or antibiotics, a reduction in the incidence of dimethylhydrazine-induced colon tumors in Fischer rats was observed. Our current plan is to administer procarcinogens and marker compounds by the oral and intracecal routes. The formation of metabolic products and mutagens will be assayed in urine and feces, and will be compared to the fecal bacterial enzymes, beta-glucuronidase, nitroreductase and azoreductase. The procarcinogens are 4-dimethylaminoazobenzene - a substrate for azoreductase, 4-amino-2', 3-dimethylbiphenyl-glucuronide - the glucuronide of an intestinal carcinogen; hydrolysis is mediated by beta-glucoronidase, beta-naphthol-glucuronide - a substrate for beta-glucuronidase; closely related to the carcinogen naphthylamine; a marker compound, naphthol-glucuronide, will test fecal beta-glucuronidase. We will alter the metabolic activity of the microflora by the following maneuvers: diet (low vs. high fat); administering antimicrobial agents (tetracycline and metronidazole); feeding Lactobacillus supplements; and giving sacchrolactone, a specific inhibitor of beta-glucuronidase. The effect of these procedures can be assessed rapidly by measuring metabolic products of the procarcinogens, mutagens and bacterial enzymes in the feces. Studies in humans will attempt to suppress fecal bacterial enzymes by feeding Lactobacilli and by giving a low dose of tetracycline. Two marker compounds will be used to determine the activity of fecal enzymes: salicylazosulfapyridine, a substrate for azoreductase, and phenolphthalein-glucuronide, a substrate for beta-glucuronidase. It is hoped that these studies will provide a useful method to assess the role of the intestinal microflora in activating several classes of procarcinogens, as well as investigating strategems to suppress bacterial metabolism in animals and humans.